In general, a construction machine includes an engine and a hydraulic system. The engine outputs power.
The hydraulic system may include a joystick, a pump, a main control valve, and an actuator.
The joystick may be manipulated according to an intention of an operator, and a pilot signal is generated by the amount of manipulated displacement.
The pump is operated by the power, so that high pressure working fluid is discharged, and the working fluid is provided to the main control valve. In the meantime, the plurality of hydraulic pumps may be provided.
The main control valve includes a plurality of valve units, and each of the valve units includes a spool. Further, each valve unit is connected with a specific actuator. Further, in each valve unit, the spool may be moved according to the pilot signal. When the spool is moved, a flow path is opened and the high pressure working fluid is provided to a specific actuator, so that the actuator is operated to enable an operator to perform desired work.
The actuator may include a left travelling motor and a right travelling motor for travelling of the construction machine, a swing motor for swinging an upper body, a boom cylinder for moving a boom up or down, an arm cylinder for dumping or clouding an arm, and a bucket cylinder for dumping or clouding a bucket.
The construction machine having the aforementioned configuration may be controlled as described below.
An operator manipulates a corresponding joystick in order to operate the desired actuator. When the joystick is manipulated, a pilot signal is generated. The pilot signal is provided to a pressure receiving unit of a specific spool provided in the main control valve. The spool is moved according to the pilot signal, and thus high pressure working fluid is provided to the specific actuator.
A loading operation among the operations of the construction machine will be described as an example. The loading operation may include a digging pattern, a boom up and swing pattern, an only swing pattern, a dump pattern, and a boom descending and swing pattern.
The digging pattern is a process of putting an operation target into a bucket, in which the bucket and the arm may be clouded. Further, a load may be increased in the digging pattern.
In the boom up and swing pattern, the boom may be ascended and the upper body may swing in the state where the operation target is put into the bucket. Further, a load may be greatly applied in the boom up and swing pattern.
In the only swing pattern, the upper body may swing in the state where the boom is maintained in the up state. Further, a load may be minimized in the only swing pattern.
In the dump pattern, the operation target put into the bucket may be put out by dumping the bucket. A general load, which is not large and is not small, may be applied in the dump pattern.
In the boom down and swing pattern, the boom is returned for the digging, and the boom may be descended and the upper body may reversely swing. In the boom down and swing pattern, a low load is applied.
In the meantime, in a control device and a control method for a construction machine in the related art, a capacity of a pump is determined in order to implement a required operation speed of the actuator regardless of a load. Because of this, a demand of the operator is matched with an operation speed of each actuator provided in the construction machine.
Accordingly, a final engine rpm is determined by adding mapping of the capacity of the pump and the engine rpm, and mapping considering each operation pattern of the operator.
However, the control device and the control method for the construction machine in the related art have problems as described below.
In the control device and the control method for the construction machine in the related art, an output of the pump is changed based on a flow rate to be discharged from the pump and each operation pattern, so that an adjustment of the engine rpm according to a change in a load is limited.
This will be described in more detail with reference to FIG. 1. FIG. 1 is a diagram for describing a change in the engine rpm according to a time when a loading operation is performed by the control device and the control method for the construction machine in the related art.
In a digging pattern, in which digging is performed, the target engine rpm may be uniform. However, the digging pattern is a process in which digging is actually performed, and a heavy load is applied, but the engine rpm is uniform, so that an output of the pump may be short. Particularly, when the output of the pump is short, there is a problem in that operation performance deteriorates.
In the meantime, in the dump pattern, the dump pattern is recognized as other patterns, so that the engine rpm is maximized That is, in the dump pattern, even though a load is not greatly applied, the large output of the pump may be output. Accordingly, in a method of controlling an excavator in the related art, fuel may be wasted in the dump pattern.
On the other hand, in the boom down and swing pattern, it is determined that a load is low, so that the engine rpm may be set to be excessively low. Accordingly, in the method of controlling the excavator in the related art, the output of the pump is low, so that a reverse swing speed is excessively low when the upper body reversely swings.
Accordingly, the control device and the control method for the construction machine in the related art may control the engine rpm so that the engine rpm may be adjusted according to a variation of a load, but when it is necessary to increase the output of the pump or the output of the pump may be decreased, the engine rpm fails to be appropriately set, so that the output of the pump is low, fuel efficiency is degraded, or an operation speed of the specific actuator is remarkably decreased.